Without more info on how the kid got into your game then we can't rally offer much more. I will give you some examples I have encountered.
I run a game for a 7 yo, a 15 yo, and 4 11 yo. The 7, 15, and one 11 yo are my sons. The other three 11 yo are friends of my middle son. This works great. The parents know us.
The DM I play with in my adult group said he ran a group for him son and the son's friends when they were young teens. Eventually th son and all the friends except one lost interest. The one join my DM's adult group at the time until he graduated and went away to college. That worked fine too.
I run a game for a 7 yo, a 15 yo, and 4 11 yo. The 7, 15, and one 11 yo are my sons. The other three 11 yo are friends of my middle son. This works great. The parents know us.
The DM I play with in my adult group said he ran a group for him son and the son's friends when they were young teens. Eventually th son and all the friends except one lost interest. The one join my DM's adult group at the time until he graduated and went away to college. That worked fine too.